String Wound filter Cartridge with high dirt holding capacity, engineered for superior performance and longer life!
Gopani’s Clarywound string wound cartridge filters use precision CNC-controlled depth filtration to capture and hold particulate contamination from 0.5 to 150 micron across a diverse range of industrial liquids. Unlike surface-type filters that trap particles only at the outer layer, string wound depth filters intercept contaminants throughout the entire cross-section of the cartridge — from outer layers through to the core. This graded density construction means the winding is progressively tighter towards the centre, so coarser particles are caught in the outer zones while finer particles are retained closer to the core. The result is a significantly higher dirt holding capacity, longer service intervals, and lower total filtration cost compared to surface or pleated media for high-turbidity streams.
Every Clarywound cartridge is wound on Gopani’s in-house CNC programmable winding machines, which precisely control yarn tension, winding angle, and layer density throughout the build. This machine consistency eliminates the variation inherent in manually wound cartridges — every cartridge in a batch delivers the same flow resistance, same particle retention, and the same service life. Yarn materials include pharmaceutical-grade polypropylene, E-glass fibre, natural cotton, and bicomponent PP/PE blends, giving process engineers the flexibility to match filter media to their specific fluid chemistry and temperature conditions.
Seven distinct variants cover everything from aggressive chemical service to food-grade applications. Use the table below to identify the right filter for your process conditions.
| Product | Filter Media | Core | Micron Range | Max Temp | Best For |
|---|---|---|---|---|---|
| Clarywound Extreme | Polypropylene yarn | Injection moulded PP (single piece) | 0.5 – 150 µm | 80°C continuous | Chemical processing, pharma intermediates, electroplating, RO pre-filtration |
| Clarywound GF | Glass fibre (E-glass) yarn | Stainless steel / PP | 0.5 – 75 µm | 120°C continuous | Hot solvents, aggressive acids/alkalis, high-temperature process streams |
| Clarywound 3X | Polypropylene yarn (triple-density) | PP | 1 – 100 µm | 60°C continuous | High-TSS feeds, applications needing 3× extended filter life and dirt holding |
| Clarywound Ultra | Polypropylene yarn | PP | 1 – 100 µm | 60°C continuous | General industrial water, cooling tower make-up, process water pre-filtration |
| Clarywound CPU | Cotton yarn | PP | 1 – 100 µm | 60°C continuous | Potable water, brewery, food & beverage, pharmaceutical water |
| Clarywound Extreme Bico | Bicomponent PP/PE yarn | PP | 1 – 50 µm | 70°C continuous | Hot-fill food applications, potable water, filtration requiring enhanced fibre bonding |
| Clarywound Cotton SS | Cotton yarn | 316L Stainless steel | 1 – 100 µm | 80°C continuous | Brewery, dairy, edible oil, pharmaceutical — wherever SS core is required for hygiene or high temperature |
A string wound cartridge is built by winding yarn continuously around a central core in a controlled diamond pattern. The critical variable is how the winding angle and yarn tension change from the outside diameter inward. Gopani’s CNC winding program begins with a wide diamond pattern and relatively low tension at the outer radius — this creates large inter-yarn voids that capture coarse suspended solids early and allow flow to pass through. As the winding builds toward the core, the program tightens progressively: the diamond angle narrows, tension increases, and the inter-yarn voids become correspondingly smaller. By the time liquid reaches the innermost winding layers, only particles below the rated micron cut-off can pass.
This graduated structure distinguishes a true depth filter from a simple wound surface filter. In a surface filter, the entire particle load accumulates at one plane, which results in rapid differential pressure rise and short service life. In a depth filter, the particle load is distributed across the radial cross-section — coarse particles are immobilised in the outer zone, mid-range particles in the mid-zone, and fine particles in the inner zone. This distribution mechanism is why well-made string wound cartridges consistently outlast pleated or melt-blown alternatives in applications with high-turbidity feeds.
Clarywound Extreme and GF are routinely specified for intermediate chemicals, process solvents, and aggressive acid or alkali streams. The all-polypropylene construction of Clarywound Extreme resists the full range of mineral acids, caustic solutions, oxidising agents, and most organic solvents. For streams above 80°C or where PP has insufficient chemical resistance, Clarywound GF with its glass fibre winding and stainless steel core is the standard choice.
Clarywound Extreme — wound from pharmaceutical-grade, extractable-free PP yarn — is widely used for pre-filtration of WFI and purified water systems, API process streams, and intermediate bulk chemical feed. Clarywound CPU and Cotton SS provide FDA-compliant cotton media for oral liquid, parenteral, and nutraceutical applications where natural fibre is preferred or specified.
Clarywound CPU (cotton/PP) and Clarywound Cotton SS (cotton/316L SS) are the preferred choices for brewery, dairy, edible oil, soft drink, and bottled water operations. Cotton fibre is inert to most food-grade fluids, NSF-compliant, and capable of achieving clarity filtration at 1–5 µm without fibre migration. The stainless steel core of the Cotton SS variant handles CIP temperatures and the mechanical loads of high-flow brewery manifolds.
String wound cartridges are the dominant pre-filter media ahead of reverse osmosis membranes. Clarywound Ultra provides cost-effective pre-filtration of municipal and borewell water at 5–25 µm. Where SDI control is critical, Clarywound Extreme at 1–5 µm provides consistent silt density index reduction to protect high-flux thin-film composite membranes. Clarywound 3X is preferred in high-turbidity raw water applications where extended service life between changeouts is the primary economic driver.
Plating bath filtration demands chemical resistance across high-concentration acid and alkali electrolytes at elevated temperatures. Clarywound Extreme at 0.5–5 µm is widely used in nickel, chrome, copper, and zinc plating circuits where particulate contamination in the bath causes surface defects. The 80°C continuous operating temperature covers most electroplating bath conditions without the cost of glass fibre media.
Clarywound 3X and Clarywound Extreme handle produced water polishing, injection water preparation, and fuel filtration in upstream and downstream operations. The high dirt holding capacity of the 3X variant reduces changeout frequency in high-TSS produced water streams, and the wide micron range of the Extreme covers both coarse solids removal (50–100 µm) and fine polishing (1–5 µm) within a single product series.
Process water quality directly affects dyeing uniformity. String wound cartridges at 5–25 µm are standard pre-filters on dyeing machine water feeds, removing iron particles, mill scale, and suspended solids that would otherwise cause uneven dye uptake or spot defects. Clarywound Extreme at 60°C to 80°C covers both ambient and heated dye liquor streams.
CNC programmable winding machines. Most commodity string wound cartridges are produced on manually set machines where winding tension and pattern are approximate. Gopani uses fully programmable CNC winding centres that execute a defined tension profile, angle sequence, and layer count for every cartridge. The winding program is specific to each micron rating, so a 1 µm Clarywound Extreme and a 50 µm Clarywound Extreme are wound to different programs — not just described differently on a label.
Continuous single piece injection moulded PP core. A weak or porous core is a common failure point in string wound cartridges under high differential pressure. Clarywound Extreme uses a continuous single piece injection moulded polypropylene core with no seams, joints, or adhesive bonds. This core will not buckle, collapse, or deform at the rated differential pressure. It also eliminates the end-cap bonding failures and core-to-endcap gap leaks that affect assembled cores.
Widest available micron range in a single series. Clarywound Extreme spans 0.5 µm to 150 µm — 14 standard ratings across a 300:1 ratio — all wound from the same PP yarn on the same core platform. This means a process engineer can specify a Clarywound Extreme at 5 µm for pre-filtration and 0.5 µm for polishing, and install both in the same housing type, with the same seal size, without sourcing from two different product families.
Matched housing ecosystem. Gopani manufactures polypropylene filter housings designed around the Clarywound OD and length standards. This eliminates the fitment compromises that arise when sourcing cartridges and housings from different suppliers and ensures predictable bypass-free sealing under operating pressure.
All Clarywound cartridges are available in the following standard sizes and configurations:
String wound cartridges are built by winding continuous yarn around a core. Melt blown cartridges are formed by extruding molten polymer fibres onto a mandrel. String wound filters typically have higher dirt holding capacity and better performance with large-particle, high-turbidity feeds. Melt blown cartridges offer better fibre migration resistance and are preferred where media shed could be an issue. For most industrial pre-filtration duties, string wound cartridges offer a lower cost per service interval.
The standard recommendation is 5 µm for municipal feed water and 1–3 µm for borewell or surface water with higher turbidity. A single-stage 5 µm Clarywound Extreme is adequate for well-coagulated municipal water with low SDI. For feeds with variable turbidity or SDI above 3, a two-stage approach — 20–25 µm Clarywound Ultra as a roughing filter, followed by 1–5 µm Clarywound Extreme as a polishing filter — gives the best membrane protection and the lowest total cartridge consumption.
Clarywound cartridges are designed for single-use service. Backwashing may partially restore flow, but the open winding structure retains fine particles deep within the media matrix that cannot be fully removed by reversing flow. For applications requiring cleanable elements, Gopani supplies pleated stainless steel or polypropylene cartridges as alternatives.
Clarywound CPU (cotton/PP) and Clarywound Cotton SS (cotton/316L SS) use food-grade cotton yarn compliant with NSF/ANSI standards for potable water contact. Clarywound Extreme (PP yarn) can also be used in potable water service — its pharmaceutical-grade PP yarn is free from extractable plasticisers, binders, or adhesives. Please request the relevant NSF/FDA compliance documentation when ordering for potable water applications.
For Clarywound Extreme in a 10 inch element, the rated flow is up to 1.2 m³/hr at clean filter conditions with water at 20°C. Flow rate scales linearly with cartridge length — a 20 inch element handles up to 2.4 m³/hr and a 40 inch element up to 4.8 m³/hr. Actual operating flow should be set at 60–70% of rated clean flow to allow for the differential pressure increase as the filter loads, without reaching the changeout threshold prematurely.
Divide your total flow rate (in m³/hr) by 1.2 to get the minimum number of 10 inch equivalent cartridges required. Then select a multi-cartridge housing (1, 3, 7, or 12 round) to suit that count. For example, a 6 m³/hr system requires 5 × 10 inch equivalent cartridges — a 7-round housing with 10 inch elements leaves one cartridge of headroom for pressure budgeting. Contact Gopani’s technical team for detailed sizing assistance including housing selection, differential pressure budgeting, and changeout interval estimation.
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Designed for condensate polishing units in power plants
Wound cartridge filters specifically designed for condensate polishing units of power plants.
Designed for Viscous Fluids and Operating Temperature Upto 120°C
Designed for Viscous Fluids and Operating Temperature Upto 120°C
High dirt holding capacity string wound cartridge filters with superior quality cotton media
9.75”, 10”, 20”, 30”, 40”, 50”, 60”, 70” in standard and jumbo sizes.
Polypropylene, Glass Filled Poly Propylene, Stainless Steel, Tinned Steel
Polypropylene, Cotton, Glass Fibre
Gopani has a state-of-the-art manufacturing facility. We have a team of filtration experts and equipment engineers who use unique CNC machines and customize them for a controlled manufacturing process. We have a thorough quality check process for all the products, whether manufactured in-house or sourced from vendors. This way we ensure that any product that moves out of our facility is of the best quality.
Gopani manufactures the best quality cartridge core, that has higher structural integrity than regular the string wound cartridge cores. The Clarywound core does not bend or buckle and provides support to the filter medium to retain the weave density and keep gradient structure intact for a long time.
Regular string wound cartridges often face problems like loosening of the weave, bending of the core and seeping of micro fibres through the filter contaminating the filtered product. The Clarywound on the other hand, has a structurally well build support core. The yarn is also tightly wound using honey comb weave on CNC machines, this means that it does not budge or loosen when it is inserted into the housing or exposed to high flows.
